/Engine/Source/Runtime/PakFile/Public/IPlatformFilePak.h
Gets a list of FullPaths (includes Mount directory) for every File in the given Pak's Pruned DirectoryIndex
void GetPrunedFilenamesInPakFile ( const [FString](API\Runtime\Core\Containers\FString) & InPakFilename, [TArray](API\Runtime\Core\Containers\TArray)< [FString](API\Runtime\Core\Containers\FString) > & OutFileList )